Horace h



H. H. WELCH March 4, 1930.

CARBURETOR Original Filed Dec. 8, 1916 Reissued Mar. 4, 1930 UNITED STATES PATENT OFFICE HORACE H. WELCH, OF DETROIT, MICHIGAN, ASSIGNOR, BY MESNE ASSIGNMENTS, '10

scams :3. came, TRUSTEE CARBURETOB Original No. 1,578,873, dated March 30, 1926, Serial 1T0. 135,723, filed December 8', 1916. Application for reissue filed December 31, 1927. Serial Ho. 244,016.

This invention relates to carburetors of the vacuum feedtype, i. e., carburetors in which a vacuum in the float chamber is maintained to draw fuel to the said float chamber from a supply tank situated at a lower level.

The particular ob'ect of my invention is to provide a vacuum eed carburetor in, which the necessary vacuum in the float chamber 15 float chamber which is always suificient to produced solely by the aspirating effect of air passing at high velocity through a Venturl or other choke tube. uum' feed carburetor the vacuum in the float chamber is produced by the vacuum existing in the intake manifold of the connected engine and as a consequence the vacuum in the float chamber is often too high, causing excessive evaporation of fuel, and often too low, as when the engine is running at low speed and full load with wide open throttle. In the improved carburetor hereinafter de scribed the vacuum in the float chamber is produced by connecting the air space of the closed float chamber to the restricted portion of a venturi through which air is passing into the mixing chamber atlhigh velocity, thus maintaining a uniform vacuum in the raise the fuel, and never great enough to cause evaporation of the lighter particles of the fuel. The particular advantage of this means of producing the vacuum in the float chamber lies inthe fact that the reduction in pressure at the constricted portion of a venturi is several times greater than at the exit end of the venturi. The latter fact is utilized in this invention to provide a vacuum feed carburetor in which the vacuum in the float chamber is several times greater than the vacuumin the intake manifold of the engine when running at low speed under load. This means that the fuel may be lifted with much less throttling of the engine than is possiblewith the ordinary type of vacuum feed carburetor.

A further object of my invention "is to provide a carburetor havin a fairly constant vacuum in the float ch'am er, thus making it possible to draw fuel from a supply tank at a lower level under all operating conditions.

A further object is to provide a carburetor In the ordinary vacferred form are hereinafter more fully described and claimed and shown in the accompanying drawings in which- Fig. 1 is a vertical section of the preferred commercial form of a carburetor embodying my invention.

Fig. 2 is a diagram illustrative of the princlple of operation involved in my improved carburetor.

The device herein shown and described differs from the device in my co-pending application. Serial No. 13,558, principally in that, in the device shown in said pending application, the fuel is supplied in variable quantity to the main air conduit by means of a nozzle situated at or near the point of greatest variation in pressure in the conduit, the variation in pressure being depended upon to vary the flow of fuel in proportion to the variation in the volume of the air passing through the air conduit per unit of time. With the device here shown the atomizer is subjected to substantially constant degree of Vacuum, the flow through the fuel conduit being varied-or controlled by a metering pin positioned variably in the conduit in accord with variations in the volume of air flowing through the'air conduit per unit of time.

The means whereby fuel is fed into the fuel chamber by a degree of vacuum is shown in Fig. 2 in which 1 indicates an air conduit of the general form of a Venturi tube and the upper end of the fuel chamber 2, above the fuel level, is in communication therewith by means of a tube 3 terminating at about the point of greatest restriction in the conduit 1. Whatever degree of vacuum is produced at this point of greatest restriction is likewise produced in the tube and in the. air space of the fuelchamber 2 which is in communication with the fuel tank by means of a tube 4. The vacuum produced in the fuel chamber is thus utilized to supply the chamber from the supply tank and the level tr fuel in the chamber is controlled by a'float 6 of common type operating a -valve'7 to close the mouth of the tube' l when the fuel has reached the desired level. By this arrangement the flow into the fuel chamber ceases upon the closing of the mouth of the tube by the valve. The tube 3 may enter the conduit 1 at any desired point preferably as shown in Fig. 2 with the open end pointing in the direction of flow of air therethrough.

In Fig. 2 is shown a second venturi 8 discharging into the main air conduit and a chamber of the carburetor.

third venturi 9 discharging into the venturi 8 at the point of greatest restriction therein.

A fuel conduit 10 discharges into the venturifl 9 at, about the'point of greatest restriction, the open end of which points in the direction .of flow of air therethrough, and this fuel conduit is connected to the bottom of the fuel The flow of fuel into the conduit from the fuel chamber is controlled by a metering pin which is connected with a valve 12 controlling the air inlet of the main air conduit, a variation in jected is less than that to which the fuel in I 0d of operation of the device.

I the fuel chamber is subjected. .The difference in pressure produces a flow of fuel into the venturi 9 and consequently, into the main air conduit of the carburetor.

The purpose of the provision of the venturi in the channel between the air space of the fuel chamber and the main air conduit is to reduce the pressure in the fuel chamber below that of the main air conduit producin a greater degree of vacuum in the cham er without resulting in an increased throttling efl'ect onthe connected engine, and by pointing the tube- 3 in the direction of the flow through the venturi 1 at the point of highest velocity of the air passing therethrough, the maximum reduction in pressure in the float chamber is produced under the given conditions.

It is to be noted that, in the commercial form shown in Fig. 1, the single .venturi is dispensed with and a multiple venturi only is used. In such case the air space is subjected to the degree of 'vacuum produced by one venturi and the fuel discharge is subjectedto the degree produced by both. The diagram Fig. 2 is believed to make clear this differential condition and the general meth- In the preferred commercialform of the invention asshown in Fig. 1, the main air conduit is indicated at 20 and is provided with a throttle valve 21 adjacent the outlet I leading into the intake manifold of the internal combustion engine (not here shown).

This mainair conduit is only open toatmosphere through an inlet normally closed by the spring controlled valve 22 and through an open Venturi tube 23, the preferable form of the conduit and position of this venturi being such that the longitudinal axis of the venturi practically coincides with the longitudinal axis of that portion of the conduit 20 in which it is located and opening in the direction of flow of air therethrough. The valve 22 is positioned in a part of the air conduit directly over the center of the fuel chamber 24 which is secured to the lower side of the conduit 20 by the screws 25. The air conduit 20 is closed to the fuel chamber and the joint between the two parts is made substantially air tight to prevent a flow of air into the fuel chamber therethrough.

The Venturi tube 23 is preferably threaded in an opening in the lower part of the main air conduit 20 and is formed with a boss 26 at the top thereof threaded to receive an end of the conical deflector member 27 terminating near the point of greatest restriction in the venturi 23. The lower end of the venturi is open to atmosphere as indicated at 28 so that air may flow freely thereinto at all times, and a double walled tubular member 29 is also positioned with the discharge end thereto at about the point of greatest restriction in the Venturi tube. This member 29 is formed of an outer cylindrical member 30 and an inner tubular mem-- ber 31 having a bell shaped outlet 32 into which the conical end of the deflector 27 extends but spaced from the wall thereof substantially as shown. The tube 31 is open to atmosphere at the bottom so that air ma flow through the tube 31 and out throug1 the bell shaped discharge end around the deflector. This bell shaped discharge-end also spaced from the end of the surrounding tube 30 as indicated, and air may flow into the conduit 35 formed between the two tubes from the apertures 33 provided therefor.

Air rushing into the venturi 23 through the encircling channel 38 formed in an extend ing portion 39 on the fuel chamber.

By the arrangement described air flowing at high velocity through the main venturi 23 from the inlets 31 and 28 tends to produce the greatest possible degree of vacuum in the conduit 35 between the two tubes. The degree of vacuum produced in the radial channels 37 and the surrounding channel 38 is still greater in' degree than in the conduit due to the action of the secondary venturi 36.

Between the channels 37 and the end of the conduit 35, a channel 40'opens thereinto 'leading from the air space at the top of the fuel chamber, and a channel 4]. leads from the bottom of the fuel chamber to the channel 38 in communication with the radial channels 37. These channels 37 are slightly above the normal level of the fuel in the fuel chamlines a-a and, by reason'of the formation of these channels 37 in the secondary venturi, the fuel in the channel 41 is subjected to a higher degree of vacuum than is produced in the upper end of the fuel chamber. The fuel is thus introduced into the channels or atomizer 37 by difference in pressure and flows into the conduit 35 at a right angle to the direction of flow of air therethrough. It is thus atomized in the tube 35 and is again further broken up on its discharge through the ring shaped discharge end 34 into the main venturi 23.

As heretofore stated, the channel 41 leads into the bottom of the'fuel chamber through avertical conduit 42. This conduit has an inlet aperture 43 after the nature of a valve seat and a pin 44 having a long taper is posi I tioned within this aperture. This pin, under normal conditions and with the valve 22 closed, does not quite contact with the wall of the aperture 43, allowing a flow of fuel therebetween sufficient to supply the engine while idling. At ordinary idling speed of operation of the engine, sufficient air is sup- I plied through the Venturi tube arrangement above described, and this metering pin is unaltered in position and flow is therefore restricted in quantity depending upon the setting of the pin 44. As the volume of air required by the engine per unit of time is increased beyohd that which the venturi tube arrangement is capable of supplying, the increased demand causes suflicient degree of vacuum in the main air conduit 20 to open the valve 22 to a greater or less extent depending upon the demand. This valve 22 is provided with a vertical stem 45 extending through the wall of the conduit 20 and into the fuel chamber and the pin 44 is threaded into the end of this. stem so that, upon the valve 22 being depressed to allow a greater volume of air into the air conduit, the metering pin is retracted from the'aperture 43 increasing the area of the space between the valve 44 and the surrounding wall by reason of the taper of the pin and thus allowing for an increased flow of fuel through the pas-' sageway. As before stated, the taper ofthey valve is a long taper andis such that the flow quired percentage of fuel to air flowing into the intake manifold of the engine, and by altering the vertical position of the pin 44 in relation to the seat 43 by screwing it into or out of the end of the stem 45 considerable variation in fuel flow may be produced, as may be required for adjustment.

The valve 22 is normally closed by means of a coiled spring 46 and in order to prevent a fluttering thereof, I preferably employ the valve cage 47 having a ring portion 48 threaded into the wall of the conduit 20 providing a valve seat. The upper end of the cage is chambered and the upper end of the valve stem is provided with a plunger 49 fitting the chamber and forming What may he termed a dash-pot, adapted to. prevent fluttering of the valve under variation in pressure in the conduit 20. While this dashpot arrangement is not essential to the operation of the carburetor I prefer to use an instrumentality of such character to prevent a fluttering of the valve which would affect the flow of fuel into the conduit .41.

valve 45 to pass therethrough, and on a fall in the level of fuel the valve 52 may lift due to the vacuum produced by means of the passageway 40 heretofore described which draws the fuel into the chamber. On the fuel reach- 'ing normal level the lever 54 connected with the float forcesthe valve on to the seat and closes'the channel 53 to the vacuum produced in the fuel chamber.

By reason of the channel 40 communicating with the Venturi tube atthe point of the greatest restriction therein the ,degree of vacuum produced in the top of the fuel chamher is greater than the degree produced in the main conduit 20. A further decrease of pressure in the conduit 41 is caused'by the secondary venturi formed in the. conduit 35 below the point of communication of the assageway 4O therewith. The quantity'of air passing the secondary venturi is slight in outlet 34. Thus the pressure in the tube i I comparison to the discharge capacity of the 35 remains practically unaffected by flow through the atomizer.

This arrangement is productive of a con-.

siderable vacuum for raising the gasoline from thesupplytank to the carburetor and at the same timedoes not unduly throttle the I engine i-. e., there is but ,a' slight degree of vacuumin the intake manifold and a considerably higher degree of'vacuum in the fuel chamber. The increased degree of vacuum in the fuel chamber, therefore, does not act as a drag on the engine.

From the foregoing description it becomes evident that my improved carburetor is comparatively simple and inexpensive to manufacture and is highly cfficient in operation by reason of embodying features of established superiority, as the metering pin controlling the fuel flow in relation to variation in volume of air demanded, and incorporating therewith such an arrangement of parts as to utilize the aspirating effect of air passing through the carburetontoproduce a flow of fuel into the fuel chamber thereof and from the fuel chamber to the atomizer. This latter-function is performed in the carburetor the aspirating effectto produce a flow of fuel thereof.

into the fuel chamber.

Having thus fully described my invention, its utility and mode of operation, what I claim and desire to secure by Letters Patent cf the United States is- 1. A carburetor comprising a casing, an anterior valve for restricting the flow of air into said casing, a pair of Venturi tubes leading into said casing, a fuel supply reservoir, one of said Venturi tubes having a suction port leading to said reservoir at a point below the fuel level thereof, the other of said Venturi tubes having asuction port leading to said reservoir at a point above the fuel level I 2. A carburetor comprising a casing, an anterior valve for limiting the air passage into said casing, a small Venturi'tube extendin g into said casing and having asuction orifice for the delivery of fuel to said casing, a second Venturi tube extending into said casing and having a suction orifice for the maintenance of a partial vacuum upon the fuel for delivery to the first Venturi tube.

3. A carburetor comprising a casing form ing theenclosure for the mixing chamber and its appurtenant air lnductlon chamber, a fuel supply reservoir, a small Venturi tube extending into the chamber of said carburetor appurtenant to the mixing chamber andhaving a suction opening connecting with 'the upper spaces ofsaid reservoir, and other means for admitting chamber.

4. In a carburetor, the combination with a supply reservoir sealed against atmos heric communication, ofa smallVenturi tu e for the passage of airinto the carburetor by the all 'of the fuel to said mixing.

suction of the suction producing means for the carburetor, said Venturi tube being provided with an opening near the throat thereof connecting with the upper space of said reservoir, whereby the partial vacuum created in the upper space of said reservoir will be maintained greater than the partial vacuum in the body of the carburetor and other means conductingall of. the fuel into the carburetor.

.5. In a carburetor the combination with a body portion forming the main air passage for the carburetor, an anterior and a posterior throttle for said passage,two Venturi tubes leading from atmosphere into said passage, a fuel reservoir, one of said Venturitubes being connected with the lower part of the fuel reservoir and serving to deliver fuel into said passage, the other of said Venturi tubes being connected with the upper space of said fuel reservoir, and serving to create a partial vacuumtherein for raising fuel from a low level source to i the fuel reservoir.

6. In a carburetor, thecombination with a body forming a main air passage, of a'large Venturi tube in 'said'passage, a small fuel delivery Venturi tube having its posterior end located at substantially the point of greatest suction in said large Venturi tube, a fuelreservoir, and a third Venturi tube having its internal end positioned at a point in said passage anteriorto the point of maximum suction of the largeVenturi tube, said third Vent-uri tube being connected for prov ducing a partial vacuum in the-upper space of the said fuel reservoir.

7. In a carburetor, a chamber adapted to be connected with the intake of an internal combustion engine, two fixed Venturitubes discharging into said chamber, said Venturi tubes being of different characteristics where by different degrees of depression obtain therein respectively when the pressure in said chamber is reduced, a constant level liquid fuel chamber, a passagewayflfor liquid fuelleading from below theliquid-fuel level in said constant level chamber to the Venturi tube in which the greater depression obtains, and a passageway leading from above the liquid fuel level in saidfconstant level chamber to the Venturi tube in .which the lesser depression obtains.

8. In a carburetor, a chamber adapted to be 7 a passageway leading from above the liquid fuel level in said constant level chamber to the Venturi tube in which the lesser depression obtains, a liquid fuel supply tank in which the level of liquid fuel isbelow the level said supply tank to said constant level chamber.

9. In a carburetor, a chamber adapted to be connected with the intake of an internal combustion engine, two Venturi tubes discharging into said chamber, said Venturi tubes being ofdifferent characteristics whereby different degrees of depression obtain therein respectively when the pressure in said chamber is reduced, a constant level liquid fuel chamber, a passageway for liquid fuel leading from below the liquid fuel level in said constant level chamber to the Venturi tube in which the greater depression obtains, a passageway leading from above the liquid fuel in said constant level chamber to the Venturi tube in which the lesser depression obtains, and a suction responsive'valve controlling air admission to said chamber.

' 10. In a carburetor, a chamber adapted to be connected with the intake of an internal combustion engine, two Venturi tubes discharging into said chamber, said Venturi tubes being of diflerent characteristics whereby dilferent degrees of depression obtain therein respectively when the pressure in said -,chamber is reduced, a constant level liquid fuel chamber, a passageway for liquid fuel leading from below the liquid fuel level in .said constant level chamber to the Venturi tube in which the greater depression obtains, and a permanent passageway leading from above the liquid fuel level in said constant level chamber to the Venturi tube in which the lesser depression obtains.

11. In a carburetor, a chamber adapted to be connected with the intake of an internal combustion engine, two Venturi tubes discharging into saidchamber, said Venturi fuel level in said constant level chamber to the Venturi tube in which the lesser de ression obtains, a liquid fuel supply tan in which the level 0 liquid fuel is below the level of liquid fuel 1n said constant level chamber, and a fuel supply passageway leading directly from said supply tank to said constant level chamber..

12. In a carburetor, achamber adapted to be connected with the intake of an internal combustion engine, two Venturi tubes discharging into said chamber, said Venturi tubes being ofdiiferent characteristics whereby diiferent. degrees of depression obtain therein respectively when the pressure in said chamber is reduced, a constant level liquid fuel chamber, a passageway for liquid fuel leading from below the liquid fuel level in said constant level chamber to the Venturi tube in which the greater depression obtains,

by the feed of fuel to said constant level fuel I chamberis by suction. v 1-3. In a carburetor of thekind described,

a mixing chamber, a fuel chamber subject to the suction of the engine through a passage.

leading thence to the mixing chamber, the juncture of said passage with the mixing chamber being so arranged that the flow of mixture passing through the mixing chamber will, by aspiration, induce in the fuel chamber a higher degree of vacuum than exists in the mixing chamber to assure the supply of fuel to the fuel chamber,-and means for delivering fuel into the mixing chamber.

14. In a carburetor, a reservoir for fuel, a chamber adapted to be connected withthe intake ofan internal combustion engine, two Venturi tubes discharging into said chamber, aclosed fuel chamber appurtenant to the-carburetor and connected toreceive fuel from said reservoir, a passage for liquid fuel leading from said fuel chamber below the level of fuel therein to one of said Venturi tubes fordelivery of fuel to said chamber, and a second passage leading from the upper region of the fuel chamber to the other Venturi tube for the withdrawal of air and fuel vapor from the fuel chamber.

In witness whereof, I hereunto subscribe my name this 24th day of December, 1927.

HORACE H. WELCH.

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